1. Field of the Invention
The present invention relates in general to an optical recording method. In particular, the present invention relates to a method for recording data onto optical discs.
2. Description of the Related Art
Formatting of data onto optical discs and error correcting process thereof are explained in FIGS. 1 and 2. The error correcting process for the DVD and an ECC block are firstly explained in FIGS. 1A and 1B.
As shown in FIG. 1A, information recorded to the DVD has a physical structure including a plurality of data sectors 20. One data sector 20 comprises, in order from the head position thereof, Identification Data (ID) 21 of a start position of the data sector 20, ID Error Detection code (IED) 22 correcting errors in ID 21, reserve data (RSV) 23, main data 24, the constituent data to be recorded, and an Error Detection Code (EDC) 25 for detecting errors in ID 21, IED 22, RSV 23, and main data 24. A plurality of data sectors arrange in sequence and constitute recording data.
Next, a process in an encoder, described subsequently, for creating an ECC block 30 by a plurality data sectors is explained in FIG. 1B. As shown, an EGG block is formed by 16 data sectors is explained in FIG. 1B. To forming the EGG format, each data sector 20 including ID 21, IED 22, RSV 23, main data 24, and EDC, each data sector having 2064 bytes arranged in an array of 12 data rows each containing 172 bytes. The first data row should start with three fields: ID, IED, and RSV, followed by 160 bytes main data. The next 10 data rows should each contain 172 bytes main data, and the last data row should contain 168 bytes main data followed by 4 bytes EDC.
For each data row, an ECC inner-code Parity (PI) 31 having 10 bytes is generated and attached to the end of the each corresponding data row to constitute one correction block 34 as shown on the right side of FIG. 1B. At this stage, correction blocks 34 with PI 31 attached are arranged in 12 lines along with the y-axis orientation. After that, the process is repeated with respect to 16 data sectors (for an ECC block). Accordingly, correction blocks 34 of 192 (=12×16) lines are obtained.
Next, 16 ECC outer-code parity (PO) 32 is respectively generated and attached to each corresponding data columns. It is noted that PO 32 also attaches to a portion of PI 31 within the correction block 34.
From the above mentioned process, one ECC block 30 including 16 data sectors is produced as shown in FIG. 1B (the right side). At this time, the total amount of the information included within one ECC block 30 is expressed by:(172+10)bytes×(192+16)lines=37856 bytes
The main data 24 (i.e., other than parity codes and data information) in it is expressed by:2048 bytes×16=32768 bytes
An ECC block 30 shown in FIG. 1B is formed by arranging 16 data sectors in an array of 192 rows of 172 bytes each. To each of the 192 rows 10 bytes of PI are added, then, to each resulting 182 columns, 16 bytes PO are added. Thus a complete ECC block has 208 rows of 208 bytes each. The bytes of this array are identified as Bi,j as shown in FIG. 1B, where I is the row number and j is the column number. For example, B1,0 indicates the first line and column zero, and B190,170 indicates the line 190 and column 170. Thus, Bi,j for i=0 to 207 and j=172 to 181 are bytes of PI 31; Bi,j for i=192 to 207 and j=0 to 171 are bytes of PO 32. Correction blocks 34 are consecutively recorded to the optical disc.
ECC block 30 comprises both PI 31 and PO 32, as shown in the right side of FIG. 1B, in order that data arranged along an x-axis orientation in FIG. 1B can be corrected by PI 31 and the data arranged along the y-axis orientation by PO 32. It is thus possible to perform error correction along both axes within the ECC block 30 shown in FIG. 1B.
More concretely, for example, if a certain correction block 34, as mentioned above, consecutively recorded to a disc, each having 182 bytes in total including PI 31, is entirely destroyed by physical damage to the disc, merely the one-byte data is lost with respect to PO 32 in one column, as viewed along the y-axis orientation. Thus, by carrying out error correction using PO 32 at each column, it is possible to accurately reproduce original information from the damaged location, even though one correction block 34 may be entirely destroyed.
The manner of actually recording a data sector included in the ECC block 30 shown in FIG. 1B is explained in FIG. 2. In FIG. 2, the bytes indicated as Bi;j corresponds to the data shown on the right side of FIG. 1B. Processes at the time of recording the data sector 20 in FIG. 2 (i.e. an interleave process and an 8-to-16 modulation process) are performed by the encoder, described subsequently.
When recording the ECC block 30 to the disc, the plurality of data rows of the ECC block 30 are firstly aligned along the x-axis orientation for each correction block 34, as shown in a top stage of FIG. 2, and are then are interleaved for division into 16 recording sectors 40 (as shown in a second top stage of FIG. 2). At this time, one recording sector 40 includes 2366 bytes (=37856 bytes/16), with a data sector 20, PI 31 and PO 32 intermingled and included in each recording sector 40. However, ID 21 (refer to FIG. 1A) in the data sector 20 positions a head portion of each recording sector 40.
The recording sector 40 is divided into a plurality of segments 41 each comprising data and having 91 bytes, with a header H appended to each (as shown in a third top stage of FIG. 2). Then, one sync frame 42 is produced from one segment 41 by 8-to-16 modulating the recording sector 40 including the paired headers H and segments 41. At this time, one sync frame 42 is composed of a header H′ and segment 43 (as shown in a bottom stage of FIG. 2). Further, data size in one sync frame 42 is expressed by:91 bytes×8×( 16/8)=1456 bytes
Then, data is written to a disc in continuous sync frames 42. At this time, one recording sector 40 includes 26 sync frames 42.
Using the disclosed physical format and recording to the disc, the 8-to-16 demodulation and de-interleaving (refer to FIG. 2) are performed when reproducing the data to thereby reproduce the original ECC block 30 while performing the effective error correction to accurately reproduce the data.
As shown in FIG. 3, U.S. Pat. No. 5,815,472 discloses an information recording apparatus that records to a DVD-R as explained previously. The following assumptions are made in the embodiment described; pre-pits or the like are formed in advance on the information tracks, to which data will be recorded. Then, at the time of recording, address information of the disc 1 is obtained by detecting the pre-pits. Thus, a record position for the disc is detected. The conventional information recording apparatus S comprises a pick-up 2, a reproduction amplifier (AMP) 3, a decoder 4, a pre-pit signal decoder 5, a spindle motor 6, a servo circuit 7, a processor (CPU) 8, an encoder 9, a power control circuit 11, a laser drive circuit 12, and an interface 13, such as an IDE bus. A data record signal SR is input through the interface 13 from an external host computer 14 to the recording apparatus S. In addition, the encoder 9 is provided with a DRAM 10.
FIG. 4 is a flowchart showing conventional DVD disc encoding. First, main data is read from the host computer 14 through the interface (IDE Bus) 13 shown in FIG. 3 and written to the DRAM 10 (S1). Next, main data restored in the DRAM 10 is read (S2). Next, the 2-byte ID Error Detection code (IED) is generated to correct errors in the 4-byte ID information (S3). Next, 6 bytes of reserve data (RSV) denoting copyright is generated (S4). Next, 4 bytes of error detection code (EDC) is generated for detecting errors (S5). Next, the data including main data. ID, EC. RSV. and EDC is scrambled (S6). Thus, a data sector is obtained. Next, 10 bytes PI is generated according to the scrambled data, and is attached to the 16 data sectors are (S7). Next, the scrambled data, ID, IED, RSV, EDC and P1 are stored to the DRAM (S8). The data stored in the DRAM is read again to generate 16 bytes PO and interleave the data sectors and PO (S9). Next, the 16 data sectors interleaving the 16 bytes PO are stored in the DRAM (S10). Thus, the data stored in the DRAM is read to be written to the disc (S11).
However, in steps S1, S2, S8, S9, S10 and S11, much data is transmitted between the optical drive IC and the memory buffer (DRAM). After reading main data from the host computer, main data (33024 (172×192) bytes) are written to DRAM (Step S1). Next, the main data (33024 bytes) is read from the DRAM (Step S2) to generate PI (1920 (10×192) bytes). Next, the main data (33024 bytes) and PI (1920 bytes) are written to the DRAM (Step S8). Next, the main data (33024 bytes) and PI (1920 bytes) are read from the DRAM to generate PO of the main data (2752 (172×16) bytes) and of the PI (160 (10×16) bytes) (Step S9). The PO (2912 (2752+160) bytes) is then written to the DRAM (Step S10), and the total data (37856 (33024+1920+2752+160) bytes) stored in the DRAM are read out for recording to the disc (S11). Therefore, a total of 176704 bytes are accessed between the drive IC and the DRAM.
Also, it is noticed that in order to generate PI (in step S7 and PO (in step S9), main data must be scrambled in advance (in step S6), the scrambled data would be stored in DRAM; as a result if there is a block that needs the same main data to record on to the same disc, thus the scrambled data in DRAM should be read out and descrambled to the original main data and then scrambled again due to the ID information being changed.
Thus, the recording speed of the optical disc is limited by the bandwidth of the memory buffer. The recording speed of the optical disc can be increased by increasing the clock rate of the memory bus, however, this increases power consumption.